This invention relates generally to brake systems and more particularly to hydraulic brake systems.
Hydraulic brakes were developed and generally perfected around the Second World War when it became necessary for airplanes to land on relatively short runways. Shortly thereafter, hydraulic brakes were incorporated into a wide variety of vehicles including trucks, cars, and the like.
In a hydraulic braking system, a brake fluid, generally made out of a petroleum product, is communicated from a master cylinder to a brake. An operator manipulates the pressure of the brake fluid by depressing a brake pedal. This depression of the pedal creates an increase in the fluid pressure from the master cylinder which causes the brake to press against a drum or disc so as to absorb the kinetic energy of the wheel. This energy absorption additionally causes the wheel to resist movement relative to the roadway. The sum of these two activities is an absorption of the vehicle's momentum causing the vehicle to slow.
One anomaly which has been observed in this braking situation is that should the brake lock onto the drum or disc, then the absorption of the kinetic energy by the brake ceases and any energy which is absorbed is between the tire and the roadway. Unfortunately, the tire/roadway absorption is much less than the brake/drum absorption so once the brake/drum lock, the slowing capability of the vehicle decreases dramatically.
To cure this problem, a variety of devices have been developed such as elaborate anti-locking systems which actually pulse the hydraulic fluid. This pulsation assures that the brake/drum never have the capability of locking. These systems are expensive to build and install and generally cannot be added later to a vehicle as an after-market device.
It has been observed that the locking of the brake/drum occurs usually at the initial outset of the contact; that is, the brake is forced into the drum at such a high pressure that a natural bonding occurs. If the initial contact were dampened or decreased slightly, then the probability of locking occurring is diminished.
To this end, several devices have been developed which dampen the pressure build-up within the brake fluid line. These include U.S. Pat. No. 3,430,660, entitled "Pressure Equalizer Apparatus for Hydraulic Brake Fluid Systems" issued Mar. 4, 1969, to Mitton; and U.S. Pat. No. 5,074,625, entitled "Adjustable Pressure Variable Response Fluid Brake Systems Regulators" issued Dec. 24, 1991, to Jones; both of these patents are incorporated hereinto by reference.
In both of these devices, a rubber bellows arrangement is used. As the pressure within the braking fluid increases, the bellows expands into a chamber of a rigid body. Once the bellows has reached it maximum extension (as defined by the chamber), the full force of the hydraulic fluid is felt by the brake; but, at the initial outset, the bellows absorbs some of the pressure and thereby dampens the braking fluids affects.
Unfortunately, in both of these devices, it is the elasticity of the rubber which is the sole determining factor in the actual dampening obtained. This factor reduces the ability to accurately and minutely engineer devices which have differing dampening qualities to fit a vehicle's specific requirements.
It is clear from the foregoing that a need exists for an adjustable and more responsive hydraulic fluid dampener exists.